<div>
    <div class="input-group mb-0" style="margin-top: 0.5rem;">
        <input type="text" class="form-control" placeholder="Recipient's username" aria-label="Recipient's username"
               aria-describedby="basic-addon2">
        <div class="input-group-append">
            <span class="input-group-text" id="basic-addon2">搜索</span>
        </div>
    </div>
</div>